Malic acid is the alternative suggested in the protocol for people who can't tolerate apple juice. Cranberry juice is another. If using apple juice, malic acid is not really necessary as there's plenty of malic acid in apple juice. I too didn't do well with plain malic acid. The recommended form is the powder, diluted in water.
Has anyone used freeze-dried cranberry juice? It would seem more convenient-- no heavy shopping bags. And no sugar.
Someone posted that they'd been using magnesium malate as softener- but can something not acidic have that effect ?